#include<stdio.h>
#include<stdint.h>
#include<fcntl.h>
#include<unistd.h>
#include<sys/eventfd.h>

int main()
{
    int efd = eventfd(0,EFD_CLOEXEC|EFD_NONBLOCK);
    if(efd<0)
    {
        perror("eventfd failed");
        return -1;
    }
    uint64_t val = 1;
    write(efd,&val,sizeof(val));
    write(efd,&val,sizeof(val));
    write(efd,&val,sizeof(val));

    uint64_t res = 0;
    read(efd,&res,sizeof(res));
    printf("%ld\n",res);

    close(efd);

    return 0;
}